Lazarus Long, the longest-lived member of the Howard Families, needs to pick up a freighter big enough to load 100,000 people and take them into orbit. Where can you go to get a good price on a space freighter?

The moon, naturally.

...Despite efforts to make the Moon colony ecologically self-sufficient, Luna City still imported vastly more tonnage than she exported. On Earth this would have resulted in "empties coming back"; in space transport it was sometimes cheaper to let empties accumulate, especially on Luna where an empty freighter was worth more as metal than it had cost originally as a ship back Earthside.

They suited up and left the dome by North Tunnel, then strolled along the grounded ships in the long, easy strides of low gravity.